The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2000-234576, filed on Aug. 2, 2000, the contents of which is herein expressly incorporated by reference in its entirety.
1. Technical Field of the Invention
The present invention relates to a battery pack having a rechargeable battery and a circuit substrate constituting a power circuit, the battery and the substrate being housed in a pack case.
2. Description of Related Art
To achieve more compact and slimmer portable information equipment, such as a cellular phone or a portable computer, batteries used therefor as power sources are required to be made more compact and slimmer. As power sources for such equipment, rechargeable batteries having high energy density are preferable. Specifically, lithium-base rechargeable batteries are suitably used. A rechargeable battery having high energy density necessitates a mechanism for protecting the battery against overcharge, overdischarge, overcurrent, and the like. Moreover, a circuit for monitoring battery temperatures and measuring battery remaining capacity is an essential mechanism when a rechargeable battery is used as power source for portable information equipment. The mechanism is constructed on a circuit substrate as a power circuit, and the circuit substrate is formed integrally with a rechargeable battery to constitute a battery pack.
FIG. 4 illustrates the structure of a conventional battery pack employing a prismatic lithium ion rechargeable battery. In this battery pack, four prismatic lithium ion rechargeable batteries 3 and two circuit substrates 5a and 5b are formed integrally together to constitute a battery block 20. Although the battery block 20 is capable of functioning as a battery power source on its own, outer packaging is necessary to ensure high handleability, sufficient insulation, safety, and the like. To secure a sufficient rigidity in the battery pack, outer packaging using a pack case for housing the battery block 20 is desirable. In this case, however, it is likely to fail to meet requirements of compactness, light weight, and slimness.
The conventional battery pack employs heat-shrinkable tubes 14 and 15 as the outer packaging of the battery block 20 in order to reduce the size and the weight of the battery pack. Specifically, the battery block 20 is covered with heat-shrinkable tubes 14 and 15 from longitudinal and transverse directions, and is then subjected to a heating treatment to shrink the tubes, thereby providing an exterior cover on the battery block 20. Consequently, a desired battery pack is realized. This battery pack is connected to the equipment in use through a connector 11 attached to the tip of a lead 13 drawn out of the circuit substrate 5a. 
However, a battery pack having its outer packaging realized by using a heat-shrinkable tube has the following disadvantages.
(1) A molding by exploiting heat contraction is structurally unstable. It is therefore inferior in dimensional accuracy and suffers from wrinkles or swells, which detracts from the appearance thereof.
(2) Heat contraction-using molding is time-consuming and is thus lacking in productivity.
(3) A heating treatment needs to be performed at a temperature higher than the softening point of the heat-shrinkable tube, which might cause heat deterioration in the members constituting the battery block.
(4) The members constituting the battery block are subjected to external pressure due to the contraction pressure exerted by the heat-shrinkable tube, and consequently suffer from a stress.
(5) Heat-shrinkable tubes are typically made from soft polyvinyl chloride and thus place a heavy load on the environment. For example, dioxin is generated by the burning of the waste.
(6) When leakage of electrolyte from the rechargeable battery occurs, the electrolyte tends to find its way into the circuit substrate, whereby the circuit might be destroyed.
(7) The circuit substrate is covered only with the heat-shrinkable tube and is thus susceptible to damage resulting from a shock or the like.
An object of the present invention is to provide a compact battery pack smaller in size and lighter in weight.
To achieve the above object, according to a first aspect of the invention, there is provided a battery pack constituted by a battery block housed in a pack case, the battery block being composed of a rechargeable battery and a circuit substrate formed integrally together, the circuit substrate constituting a power circuit. The pack case includes upper and lower cases formed from a thin-walled resin sheet, and shaped half-shell rectangular parallelepiped with their one sides coupled to each other by a hinge. The battery block is housed in the pack case folded in two on the hinge, and the side surfaces of the upper and lower cases are joined together by placing a strip of tape. In the pack case, the upper and lower cases are formed integrally together, which allows the battery pack to be fabricated simply by housing the battery block in the pack case, closing it at the hinge, and securing the pack case with the strip of tape, so that the workability improves.
According to a second aspect of the invention, there is provided a battery pack constituted by a battery block housed in a pack case, the battery block being composed of a rechargeable battery and a circuit substrate formed integrally together, the circuit substrate constituting a power circuit. The pack case includes upper and lower cases formed from a thin-walled resin sheet, and shaped half-shell rectangular parallelepiped with their one sides coupled to each other by a hinge. The pack case is folded in two on the hinge so as to accommodate the battery block composed of a flat prismatic rechargeable battery and a circuit substrate disposed on the surface of the thickness-direction side of the rechargeable battery formed integrally together. The side surfaces of the upper and lower cases are joined together by placing a strip of tape. The use of a flat prismatic rechargeable battery helps reduce the thickness of the battery block. The battery pack is fabricated simply by housing the battery block in the pack case formed of the upper and lower cases formed integrally together, closing it at the hinge, and securing the pack case with the strip of tape. That is, a slim and compact battery pack is fabricated with high workability.
These and other objects and characteristics of the present invention will become further clear from the following description with reference to the accompanying drawings.